Vehicles using all six cylinders in all operating conditions suffer from inefficiencies. For example, when stoichiometric air to fuel ratios are required for engine operation, such as in gasoline systems, there are operating conditions where excessive fuel consumption occurs. Full fueling to all cylinders in low load, idle, coast, or ranges of cruise conditions results in overuse of fuel. These low operating conditions do not need optimal engine output.
Likewise, in diesel systems, there are situations where the amount fuel being used is in excess of that necessary to power an engine. It is desirable to reduce fuel consumption.